Durable outdoor inkjet inks

ABSTRACT

An inkjet ink for printing durable outdoor images with an inkjet printer includes an basic pH aqueous ink vehicle comprising water, a soluble base, and at least one water soluble organic solvent; a pigment dispersion; and a polymer comprising base neutralized carboxylic acid groups with a glass transition temperature between 0 and 150° C. and an acid number between 50 and 1000 mg KOH/g dissolved in the vehicle, wherein the carboxylic acid groups are base neutralized; a poly-electrophilic functionalized compound capable of crosslinking the neutralized carboxylic acidic groups on the polymer wherein the ratio of the poly-electrophilic groups on the functionalized compound to carboxylic acid groups on the polymer is 1:1 or less on an equivalent basis and the ink maintains a stable viscosity and pigment particle size distribution for 6 weeks at 60° C.; the water in the ink inhibiting the crosslinking reaction until after the ink is printed and the water is substantially removed from the ink by drying.

PRIORITY INFORMATION

The present application is a continuation application of PCT PatentApplication Number PCT/US2019/061898, filed on Nov. 17, 2019, and claimspriority, under 35 U.S.C. § 120, from PCT Patent Application NumberPCT/US2019/061898, filed on Nov. 17, 2019. The entire content of PCTPatent Application Number PCT/US2019/061898, filed on Nov. 17, 2019, ishereby incorporated by reference.

PCT Patent Application Number PCT/US2019/061898, filed on Nov. 17, 2019,claims priority, under 35 U.S.C. § 119(e), from U.S. Provisional PatentApplication No. 62/768,883, filed on Nov. 17, 2018.

The present application claims priority, under 35 U.S.C. § 119(e), fromU.S. Provisional Patent Application No. 62/768,883, filed on Nov. 17,2018. The entire content of U.S. Provisional Patent Application No.62/768,883, filed on Nov. 17, 2018, is hereby incorporated by reference.

BACKGROUND

Digital inkjet printing has been rapidly replacing analog printing ofgraphic images, information signage, and photographs. The transitionfrom analog to digital started with indoor print applications but is nowgrowing into many outdoor print applications. Aqueous inkjet inks havebeen widely used for such indoor print applications while solvent and UVcurable inkjet inks have been used for both indoor and outdoor graphicalprinting due to their higher durability. In addition to the greateroutdoor durability of solvent and UV curable inkjet inks, they may beprinted directly on to a wide variety of outdoor durable substrateswithout the need for an ink receptive layer.

Pigmented aqueous inkjet inks prepared with soluble resin binders areused for printing onto a wide variety of substrates. The pigment-basedcolorants used in these inks are much more resistant to fade thandye-based colorants and are thus suitable for applications requiringexposure to direct sunlight.

However, because the water soluble resin binder in these inks mayre-dissolve when exposed to moisture, these inks are not suitable formany outdoor display applications, especially on uncoated substrates.When Pigmented aqueous inkjet inks are printed onto outdoor durablesubstrates which do not have an ink receptive layer, the image substratewill exit the printer in a wet state and be easily damaged.

Aqueous, pigmented, latex inkjet ink technology began to be utilized inan effort to improve the durability of inkjet prints, see for exampleU.S. Pat. Nos. 6,019,828 and 6,177,498.

The use of latex polymer particles in printing inks is well known.European Patent Number EP0068903B1 discloses the use of dye containinglatex particles in inkjet ink; polymeric latex particles in inkjet inksare also disclosed in published Japanese Patent Application Number2,867,491 and U.S. Pat. No. 5,284,894. U.S. Pat. No. 5,112,399 disclosesthe use of styrene-acrylate emulsions and styrene-butadiene latex ininkjet inks.

U.S. Pat. No. 5,284,894 discloses that “a volatile base, or alkalinematerial is required in a fortified latex to maintain thepolyelectrolyte resin in solution. Preferably, this base is ammonia,because it is volatile and relatively inexpensive. The ready evaporationof ammonia favors faster drying and guarantees quick development ofwater resistance that most of the inks must acquire after printing.Other volatile bases include any of the lower boiling amines such asmethyl amine, dimethyl amine, trimethyl amine, ethyl amine, diethylamine, and triethyl amine. Monoethanol amine, diethanol amine, andmorpholine can also be used to achieve special effects such as betterredispersibility on the press or slower drying. Sodium hydroxide,potassium hydroxide, sodium carbonate and other inorganic bases may beuseful for special applications. The amount of a volatile base used mustbe sufficient to maintain solubility and uniformity of the ink, withoutsettling out of the resin polyelectrolyte. We have found a pH of 8.0 to8.5 to be a preferred range.

World Patent Application Number WO1999023182A discloses latex binders as“particles” and not as solution polymers. U.S. Pat. No. 8,114,923discloses that the term “latex” or “latex dispersion” includes bothlatex particulates as well as the aqueous medium in which the latexparticulates are dispersed.

The term latex is widely used to refer to a dispersion or suspensions ofpolymer particles in a liquid medium. The use of the term latexdifferentiates the state of the polymer in the liquid ink. Whereas apolymer which is soluble in a liquid is considered to be in the liquidstate once dissolved in the liquid, the latex polymer is clearly in thesolid state as in insoluble particle suspended in a liquid.

The terms emulsion and latex are frequently interchanged. U.S. Pat. Nos.5,990,202; 6,019,828; 6,498,202; 6,417,249; 6,858,301; 7,030,175;7,371,273; 8,267,505; 8,268,910; 8,314,163; 8,487,036; 8,573,761; and8,939,568 disclose the use of polymers dispersed in a liquid inkjet ink.The entire contents of U.S. Pat. Nos. 5,990,202; 6,019,828; 6,498,202;6,417,249; 6,858,301; 7,030,175; 7,371,273; 8,267,505; 8,268,910;8,314,163; 8,487,036; 8,573,761; and 8,939,568 are hereby incorporatedby reference.

These patents use a variety of terms to describe such dispersedpolymers, for example they are called latex binders, core/shellpolymeric binder, polymer particles, latex particles, latexparticulates, polymeric latex binder, latex dispersion, stericstabilized latex particulate, self-dispersed latex particulates,polymers dispersed in a jettable vehicle, hybrid latex, core-shellpolymers and so forth. All of these the descriptions of polymerparticles dispersed in a liquid inkjet ink shall be considered latexpolymers for the purposes of this document.

Pigmented aqueous inkjet inks prepared with latex binders have achievedsufficient durability for many outdoor display applications. U.S. Pat.No. 7,030,175 discloses that in addition to the typical color andgeneral image fade issues that occur in many ink-jet ink systems,ink-jet prints have also been known for poor durability when exposed towater or high humidity. This results from the use of water-soluble andwater dispersible colorants within the water-based ink. In response tothis problem, latex polymers that are compatible with ink jet inks havebeen incorporated with the inks. The latex can consist of small micronor submicron hydrophobic polymeric particles of high molecular weightthat are dispersed in the aqueous ink-jet ink. When printed as part ofan ink-jet ink, a latex component of the ink can form a film on a mediasurface after drying, entrapping, and protecting the colorant within thehydrophobic print film.

U.S. Pat. No. 6,417,249 discloses aqueous pigmented inkjet inks whichutilize Core-Shell latex binders comprised of monomers which whenpolymerized as homopolymers form low glass transition temperaturepolymers. These binders improve film formation of the dried inkjet inksto help improve durability. This patent claims core-shell binders withglass transition temperatures which range from about −25 to +110 C. Thispatent does not disclose how the monomers in the core-shell binders aredistributed between the core and the shell. However, it would beexpected that those binders with good film formation properties wouldhave lower Tg monomers concentrated in the shell as this is the portionof the latex particle which would be expected to play the largest rolein particle coalescence and film formation.

The addition of elevated temperature drying capability to inkjetprinters has enabled latex containing inkjet inks to be printed anddried directly onto uncoated outdoor durable substrates to form printedimages with high moisture resistance. However, if the drying temperaturerequired for such inks is too high, the process will become incompatiblewith many of the polymeric film substrates used for outdoor graphicalprinting. If the drying time is too long for such inks the productivityof the printer will be diminished. Consequently, the latex polymers usedin such inks typically have low film forming temperatures to facilitatequick drying at reasonable temperatures.

It is well known by those skilled in the art that latex polymers withlow glass transition temperatures (Tg) also have low film formingtemperatures. Dried films of such polymers tend to be softer and moreelastomeric by nature than higher Tg polymers. Latex binders with lowfilm forming temperature coalesce quickly into softer films than higherTg binders. The scratch and abrasion resistance of images printed withsuch latex containing inkjet inks can be rather poor.

U.S. Pat. No. 10,072,166 discloses that the minimum film-formingtemperature (MFFT) of the latex binder in a thermal inkjet ink has to below (<100° C.) so that the film formation after printing can be achievedeasily—the lower the MFFT, the greater the ease of film formation.Consequently, it will save the energy cost of fusing of the latexparticles and increase the speed of printing. The entire content of U.S.Pat. No. 10,072,166 is hereby incorporated by reference.

The outdoor durability of pigmented aqueous inkjet inks may be improvedby selecting resin binders which have low water solubility in theirnative state but can be solubilized in high pH aqueous vehicles furtherimproves outdoor durability. Preferably, such polymers have an acidnumber greater than 50 (mg KOH/g).

Resin binders which can be solubilized into basic pH aqueous vehicleshave the advantage of forming films upon removal of the aqueous vehiclein the drying process. Inks containing solubilized resin binders may bedried under ambient conditions and form tough, abrasion resistant film.However, the drying process may be greatly accelerated by exposing theprinted ink to heated air and/or radiant infrared or near-infraredemissions.

The outdoor durability of pigmented aqueous inkjet inks prepared withsoluble polymer binders may be improved with the introduction ofcrosslinking agents to the ink. Crosslinking agents capable of reactingwith the polymer binder after printing and drying of the ink are knownby those skilled in the art, see for example U.S. Pat. No. 9,771,488.U.S. Pat. No. 9,771,488 discloses that printed ink drying methods mayinclude, for example, “a heat source (e.g., a heat press) or heated airblown from a heat source (e.g., IR heater, a hair dryer, oven, etc.)”The entire content of U.S. Pat. No. 9,771,488 is hereby incorporated byreference. The crosslinking of water soluble polymer binders greatlyreduces water solubility of such polymers by forming a 3-dimensionalpolymer network of very high molecular weight. Printed and dried inkjetinks comprised of crosslinked polymer networks have high resistance towater and other solvents and good scratch and abrasion resistance.

As used herein, the phrase “crosslinking agent” refers to a substancethat promotes or regulates intermolecular covalent, ionic, hydrophobicor other form of bonding between polymer chains, linking them togetherto create a network of chains which result in a more elastic and/orrigid structure. Crosslinking agents, contain at least two reactivegroups that can interact with respective groups present in the polymerbinder of the ink composition.

Japanese Patent Application Number 2002121447A discloses aqueous,pigmented inkjet inks which contain water soluble binders andcrosslinkers. After drying, these crosslinkers would be expected toimprove the durability and water resistance of such inks when comparedto similar inks without crosslinkers. However, this patent applicationdid not test the stability of such inks when exposed to hightemperatures. Inks must withstand commercial shipping temperatures whichcan get as high as 40° to 60° C. to have good commercial value. Undersuch hot conditions the inks disclosed in this patent application wouldbe expected to be unstable.

Much work has been done on the crosslinking of inkjet inks for improveddurability; see for example, U.S. Pat. No. 4,285,690. However, not muchattention has been paid to the stability and raw stock keeping of suchinks. The entire content of U.S. Pat. No. 4,285,690 is herebyincorporated by reference.

Crosslinking agents, which are activated during high temperature curing,have been disclosed in inkjet inks; see for example, U.S. Pat. No.9,611,401. However, such crosslinking agents typically must be activatedabove 80° C., a temperature too high for many of the substrates used inoutdoor durable graphics. The entire content of U.S. Pat. No. 9,611,401is hereby incorporated by reference.

U.S. Pat. No. 9,771,488 discloses the use of crosslinking agents whichreact with carboxylated polymers. Examples of such crosslinking agentsinclude carbodiim ides, oxazolines, melamine-formaldehyde resins, andzirconium carbonate salts. There are two main challenges for inkjet inkscontaining such crosslinking agents and soluble polymer binders; inkstability and compatibility with thermal inkjet printheads. From the inkstability standpoint, the reactions of crosslinking agents and polymersare both concentration and temperature dependent. Such reactions canproceed in the liquid ink under ambient conditions, albeit at a slowrate. However, even minor reactions in the liquid ink can alter theviscosity of the ink which in turn can degrade its printing performance.To moderate such crosslinking reactions in the liquid ink, the '488patent discloses the use of inhibitors in the liquid ink.

These inhibitors interfere with the crosslinking reaction, helping theinks to maintain a stable viscosity in the liquid state. After printing,the inhibitors may be removed from the ink as it dries, allowing thecrosslinking reaction to proceed. U.S. Pat. No. 9,771,488 disclosestertiary amines as inhibition agents of the crosslinking reaction ofcarboxyl containing polymer binders and crosslinking agents. The entirecontent of U.S. Pat. No. 9,771,488 is hereby incorporated by reference.

From an inkjet printhead standpoint, the crosslinkers disclosed in U.S.Pat. No. 9,771,488 are not compatible with thermal inkjet printheads,even with the tertiary amine stabilizers included in the ink. Use ofsuch inks in thermal inkjet printers quickly degrades the thermalprinthead's ability to eject ink from the head. Additionally, tertiaryamine stabilizers added to inkjet inks may actually catalyze thecrosslinking reaction between carboxylated polymer binders andcrosslinking agents.

Not wishing to be bound to any particular theory, it is believed thatwhen inks containing such crosslinkers come in contact with the heatingelements of thermal print heads, an insoluble material forms in the inkand is deposited on the inner surfaces of the printhead, reducing thevolume on ink accessible to the heaters and interfering with heat flowfrom the heaters into the ink.

For inkjet inks printed, using inkjet printers utilizing piezo typeprintheads, the interference of crosslinking agents which can react withcarboxylated polymers is much diminished. However, it remains criticalthat inkjet inks, containing reactive crosslinkers and binders haveadequate ink stability.

U.S. Pat. No. 6,639,006 discloses the use of poly-nucleophilicfunctionalized compounds as crosslinkers for inkjet inks containingwater-dissipatable precursors(s) for acrylic-polymers. The inkjet inksof U.S. Pat. No. 6,639,006 preferably comprise dyes as the colorants dueto their greater stability and lower loading requirements. U.S. Pat. No.6,639,006 preferably calls out a thermal inkjet printing process butdoes not preclude the use of piezo and other non-thermal printingprocesses.

Indeed, U.S. Pat. No. 6,639,006 acknowledges that the thermal inkjetprinting process may be more onerous on the precursor than othernon-thermal inkjet printing processes. In fact, U.S. Pat. No. 6,639,006states that the disclosed inks have a low tendency to block the nozzlesof thermal ink jet printers, indicating that there is still sometendency of these inks to block printhead nozzles. U.S. Pat. No.6,639,006 discloses polymeric precursor(s) with acid numbers preferablyin the range of 100 to 1000 mg KOH/g. U.S. Pat. No. 6,639,006 alsoacknowledges that water dissipatable polymers are known to work poorlyin thermal inkjet printers. Indeed, those skilled in the art willunderstand that as the acid value of a polymer increases, the polymerbecomes more hydrophilic and the viscosity of the aqueous based vehiclein which they are dissolved will become higher. For compatibility withanionically stabilized pigment dispersions, such acid polymers much beneutralized. As the acid number of such polymers is increase, theconcentration of ions used to neutralize the polymer also increases inthe ink vehicle, interfering with thermal ink jettability. The entirecontent of U.S. Pat. No. 6,639,006 is hereby incorporated by reference.

From a printer compatibility standpoint many disclosures endorse thecompatibility of inks comprised of low acid number polymers. U.S. Pat.No. 10,005,876 discloses that inkjet ink comprising polymeric binders oflow acid number (10 mg/g to about 50 mg/g) are believed to improve thedecap performance and print reliability of the inkjet ink. However, asthe acid number is reduced, it is difficult to dissolve such polymers ina basic pH aqueous vehicle. In fact, the polymers described in this the'876 patent are dispersions rather than solution polymers. As notedearlier in this document, inkjet ink containing latex or dispersion typeresins must be dried at temperatures sufficient to cause the latex ordispersed polymer to form into a film. Latex or dispersed polymers withlow film formation temperatures often suffer from low durability,particularly resistance to scratching and abrasion. Latex or dispersedpolymers with high film formation temperatures provide greaterdurability but the film formation temperatures are too high for use onsome outdoor durable substrates. The entire content of U.S. Pat. No.10,005,876 is hereby incorporated by reference.

U.S. Pat. No. 7,838,574 discloses acrylic polymers with low acid numbersin the range of 130 to 200 mg KOH/g. The entire content of U.S. Pat. No.7,838,574 is hereby incorporated by reference.

European Patent Number 2,341,110 discloses that it is preferable thatthe carboxyl group-containing polyurethane obtained in this manner havean acid value of 20 to 70 mg KOH/g since the ejection stability of theprepared aqueous ink for inkjet recording is favorable. European PatentNumber 2,341,110 discloses that the aqueous polymer prepared from thecarboxyl group-containing polyurethane that is used forms an aqueousdispersion. The particle size of the aqueous dispersion is preferablyless than 50 nm. When the particle size is 50 nm or larger, dispersionstability of the aqueous dispersion becomes unsatisfactory, and thecarboxyl group-containing polyurethane may be precipitated from the inkto cause kogation when ink is discharged for a long time. The entirecontent of European Patent Number 2,341,110 is hereby incorporated byreference.

U.S. Pat. No. 8,198,391 discloses the ejection stability of an aqueousink for ink jet is superior when the acid value of the carboxylgroup-containing polyurethane binder of the ink is from 20 to 70 mgKOH/g. U.S. Pat. No. 8,198,391 discloses that the aqueous polymerprepared from the carboxyl group-containing polyurethane that is used inthe present invention forms an aqueous dispersion. The entire content ofU.S. Pat. No. 8,198,391 is hereby incorporated by reference.

U.S. Pat. No. 8,474,963 discloses that with polyurethane and polystyreneacrylate polymeric binders with acid values above of more than 100 mgKOH/g are used in inkjet inks, problems occur such as the viscosity ofthe ink becoming excessively high, lowering ejection performance. Theresins described in U.S. Pat. No. 8,474,963 are dispersed in the inkvehicle and not dissolved. The entire content of U.S. Pat. No. 8,474,963is hereby incorporated by reference.

Published United States Patent Application Number 2007/0259989 disclosesthe use of β-hydroxyalky amide yl crosslinkers and acidic resin bindersin aqueous, pigmented inkjet inks. The ratio of the number ofequivalents of hydroxyl of the β-hydroxyalky amide yl to the number ofequivalents of acid groups and acid salts of the polymeric binder andpolymeric dispersant in the ink was generally from about 1/0.01 to about1/1. An excess of equivalents of hydroxyl to the equivalents of carboxyland salt from the binder and dispersant was preferred.

Such high levels of crosslinker are not compatible with thermalprintheads, causing a reduction in jetting efficiency as the ink isprinted through the printhead. Additionally, such high levels ofcrosslinker greatly reduce ink stability.

Indeed, Published United States Patent Application Number 2007/0259989discloses that the stability of the inks were tested by heating them to70° C. for 7 days and if key properties such as particle size of thepigment dispersion and ink viscosity did not change by more than 20%,the inks were considered to be stable. The examples tested for stabilitydid indeed change in viscosity and pigment particle size after beingsubjected to such storage conditions and such changes in theseproperties were realized. Changes in such physical properties by 20% orless can be detrimental to the printing performance of such inks. Theentire content of Published United States Patent Application Number2007/0259989 is hereby incorporated by reference.

Thus, it is desirable to provide a pigmented, aqueous inkjet ink whichwhen inkjet printed and dried on various substrates forms an outdoordurable image that improves low scratch and abrasion resistance of latexbased inkjets inks as well as improves ink stability and inkjetprinthead compatibility of crosslinker containing inks.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings are only for purposes of illustrating various embodimentsand are not to be construed as limiting, wherein:

FIGS. 1 and 2 illustrate tables of example inks;

FIGS. 3 through 5 illustrate tables showing rub resistance of some ofthe example inks of FIGS. 1 and 2;

FIG. 6 illustrates a table showing resistance to dry rub of some of theexample inks of FIG. 1;

FIG. 7 illustrates a table showing resistance to water rub of some ofthe example inks of FIG. 1;

FIG. 8 illustrates a table showing resistance to window cleaner rub ofsome of the example inks of FIG. 1;

FIG. 9 illustrates a table showing resistance to isopropyl alcohol rubof some of the example inks of FIG. 1;

FIGS. 10 and 11 illustrate tables showing ink keeping stability of theexample inks of FIG. 1;

FIGS. 12 and 13 illustrate tables showing particle size distribution ofthe example inks of FIG. 1;

FIG. 14 illustrates a table of example inks;

FIG. 15 illustrates a table showing rub resistance of the example inksof FIG. 14;

FIG. 16 illustrates a table of example inks;

FIG. 17 illustrate a table showing ink keeping stability of the exampleinks of FIG. 16;

FIG. 18 illustrates a table showing particle size of the example inks ofFIG. 16;

FIG. 19 illustrates a table of example inks; and

FIG. 20 illustrates a table showing particle size and viscositystability of the example inks of FIG. 19.

DETAILED DESCRIPTION

The following is a detailed description of aqueous, pigmented inkjetinks comprising water soluble polymeric binders and crosslinking agentsand having excellent ink stability at elevated temperatures and can beinkjet printed and dried onto uncoated substrates to form water andabrasion resistant images.

Polymers may include any carboxyl-group containing polymer that reactswith the water stabilized electrophilic cross-linking agents disclosedherein. The reactivity of electrophilic crosslinking agents tocarboxylated polymers is sensitive to the concentration of water in theink. As water is removed from the ink in the drying process, theconcentration of crosslinking agent relative to the carboxylated polymerincreases, shifting the equilibrium toward the crosslinking reaction.

Conversely, as the ink is diluted with water the equilibrium shiftstowards less interaction between the polymer and crosslinking agent.Unexpectedly, the impact of this chemical reaction equilibrium has beenobserved in the particle size distribution (PSD) of the pigmentdispersions in these inks, especially in highly reactive electrophiliccrosslinking agents.

Without subscribing to any particular theory, the reaction between theelectrophilic crosslinking agent and the carboxyl-group containingpolymer in the ink creates a macro-molecule which destabilizes thepigment dispersion, causing an aggregation of pigment particles.

Inks absent the electrophilic crosslinker have a mono-modal PSD.Depending upon electrophilic crosslinker reactivity, concentration inthe ink, and the temperature of the ink, when such crosslinkers areintroduced into inkjet inks containing carboxyl-group containingpolymers and pigment dispersions, a bi-modal or tri-modal PSD of pigmentparticles develops, with peaks at the original PSD of the pigmentdispersion and at larger PSD's. The larger PSD modes are observed toregress towards the original PSD as the ink is diluted with water.

Inkjet polymers may include, but are not limited to, a styrene-acryliccopolymer, a styrene-methacrylic acid copolymer, a maleic resin, amaleic anhydride-modified polymer, a carboxylated polyurethane, acarboxylated styrene-butadiene block copolymer, a carboxylatedstyrene-butadiene-styrene block copolymer, a carboxylatedstyrene-isoprene-styrene block copolymer, a carboxylated polyolefin, andcombinations thereof.

Examples of commercially available polymers include, but are not limitedto Bondthane™ series from Bond Polymers, NeoRez™ and NeoCryl™ seriesfrom Royal DSM N.V., Luciden™ series from Hydrite Chemical Company,Plextol™ R 123 from Synthomer, Dispertex™ series from Diamond, Takelac™series from Mitsui Chemicals America, Inc., AC and U series fromAlberdingk Boley, Inc., R series from Essential Polymers, Texicryl™series from Scott Bader, Ltd., Appretan™ series from Clariant, Hycar®,Hystretch®, Permax®, and Sancure® series from Lubrizol Corporation,Encor® series from Arkema, Inc., Arolon® series from Reichhold,RUCO-COAT®, RUCO-PUR®, and RUCO-BOND® series from Rudolf-Duraner,Witcobond® series from LANXESS, Joncryl® (available from BASF), ISOBAM®(available from Kuraray Co., Ltd), SUPERCHLON® (available from NipponPaper Chemicals), Auroren® (available from Nippon Paper Chemicals),Erkamar® (available from Robert Kraemer GmbH & Co. KG), SMA® (availablefrom Cray Valley USA LLC), XIRAN® (available from Polyscope PolymersB.V.), WorleeSin® (available from Worlee-Chemie GmbH), CRAYVALLAC®(available from Cray Valley USA LLC), MICHEM® (available fromMichelman), SBLatex® (available from Asahi Kasei Chemicals), HITEX®(available from Hansol Chemical), RL® (available from RLA Polymers PTYLTD), UNIBOND® (available from Unichem, Inc.), Hybridur® (available fromAir Products), Alberdingk® (available from Alberdingk Boley), Bayhydrol®(available from Bayer Material Science), Ecrylic® (available fromEcronova Polymer), Acropol® (available from Kros Link), Jonrez®(available from Meadwestvaco), Liocryl® (available from Synthopol),WorleeCryl® (available from Worlee), Cydrothane® (available from Cytec),Hauthane® (available from Hauthaway), Urotuf® (available fromReichhold), Picassian® (available from Picassian Polymers), and Incorez®(available from Incorez Ltd). In some embodiments, the polymer mayfunction as a dispersant for the pigment.

In some embodiments, the amount of polymer (by weight) in the inkjet inkmay be between about 0.1% and about 2.0%.

Water-soluble polymeric binders may be any of those soluble in anaqueous solution in which an amine or base has been dissolved. It maypreferably be those having a weight average molecular weight rangingfrom 1,000 to 200,000, and more preferably from 3,000 to 50,000. It mayalso be used in combination of two or more kinds. It may specificallyinclude polymers, acrylic copolymers, styrene/acrylic acid copolymer, astyrene/acrylic acid/alkyl acrylate copolymer, a styrene/maleic acidcopolymer, a styrene/maleic acid/alkyl acrylate copolymer, astyrene/methacrylic acid copolymer, a styrene/methacrylic acid/alkylacrylate copolymer, a styrene/α-methylstyrene/acrylic acid copolymer, astyrene/α-methylstyrene/acrylic acid/alkyl acrylate copolymer, astyrene/maleic acid half ester copolymer, a vinylnaphthalene/acrylicacid copolymer and a vinylnaphthalene/maleic acid copolymer, or salts ofthese, and polyurethanes.

Water soluble styrene-acrylate binders have been used in inkjet inksbefore the development of latex inks. U.S. Pat. No. 5,172,133 disclosedthe use of styrene/acrylic acid/ethyl acrylate copolymer binders in apigmented inkjet ink composition. The entire content of U.S. Pat. No.5,172,133 is hereby incorporated by reference.

The polystyrene-co-acrylate copolymer resin binder preferable has aglass transition temperature between 0° C. and 150° C., a molecularweight less than 20,000 and an acid number between 50 and 400 mg KOH/g.

The binder does contain carboxylic acid groups which give the polymer ananionic charge in the ink vehicle. The binder is not cationic and doesnot contain cationic groups. The binder forms a clear, viscous solutionwhen dissolved into the liquid ink vehicle. When the binder is dissolvedinto the ink vehicle, it does not form a dispersion, latex, core-shellparticle or the like.

While not wishing to be bound by any particular theory, it is believedthat the polymeric binder dissolves fully into solution, forming tiny,vehicle swollen “gel-coils” of a single polymer molecule each, the sizeof which is estimated to be in the range of 5 to 25 nm.

The aqueous pigmented ink contains one or more water soluble copolymerbinders. It is know that copolymer binders may be prepared with somewhatdifferent copolymer compositions and/or with different average molecularweights and yet can still be considered “structurally related polymers.

By way of example, when copolymer binders are polymerized, a mixture ofpolymer molecules which differ slightly from one another in copolymercompositions and molecular weight (chain length) is formed, all suchcopolymer molecules being a part of the same population. Such homologousmixtures of molecules are normal for copolymers and should not beconfused with heterologous mixtures of different but “structurallyrelated polymers” which may be formed in separate polymerizationprocesses and then combined together to form a mixture.

U.S. Pat. No. 9,771,488 discloses the following crosslinking agents ascapable of undergoing a crosslinking reaction with carboxyl-groupcontaining polymers: “carbodiimides reagent, a water-dispersible polymerthat contains a carbodiimide group, an oxazoline reagent, awater-dispersible polymer that contains an oxazoline group, a methylatedmelamine-formaldehyde resin, or a zirconium carbonate salt, such asammonium zirconium carbonate and potassium zirconium carbonate. Examplesof commercially available crosslinking agents include, but are notlimited to, Zirmel® (available from MEL Chemicals), Berset® (availablefrom Bercen), Cymel® (available from Cytec), WorleeMin® (available fromWorlee), Luwipal® (available from BASF), Zoldine® (available from DowChemical), Solucote® (from DSM NeoResins), Carbodilite™ (available fromNisshinbo Chemical Inc.), Resimene® & Maprenal® (available from INEOS),RODA Link® (from TFLUSA), Aerotex® (available from Union Ink), Epocros®(available from Nippon Shokubai Co., Ltd.), and Permutex® (availablefrom Stahl USA Inc.)”.

U.S. Pat. No. 5,172,133 discloses the use of two or more polymers asdispersants and binders for the pigment in an aqueous inkjet ink. WhileU.S. Pat. No. 5,172,133 does not use the term structurally relatedpolymers, U.S. Pat. No. 5,172,133 does disclose polymers which arestructurally related, for example, a styrene/acrylic acid copolymer anda styrene/acrylic acid/alkyl acrylate copolymer.

Various surfactants and dispersants useful in inkjet inks are disclosedin Published US Patent Application Number 2018/0118963. The entirecontent of Published US Patent Application Number 2018/0118963 is herebyincorporated by reference.

Surfactants and dispersants may be included in the aqueous pigmentedink. Surfactant can enhance the wetting of the composition or change theinteraction of the ink with either the printing substrate, such as afilm, or with the inkjet printhead. Various anionic, cationic, andnonionic dispersing agents can be used in conjunction with the inkvarious ink phases, and these may be used neat or as a water solution.

In one embodiment, the total surfactant concentration present in anamount that ranges from 0.05% to 5%, e.g., an amount ranging from 0.1%to 5%, or from 0.5% to 2%, by weight relative to the total weight of theinkjet ink composition.

Representative examples of anionic dispersants or surfactants include,but are not limited to, higher fatty acid salts, higheralkyidicarboxylates, sulfuric acid ester salts of higher alcohols,higher alkyl-sulfonates, alkylbenzenesulfonates, alkylnaphthalenesulfonates, naphthalene sulfonates (Na, K, Li, Ca, etc.), formalinpolycondensates, condensates between higher fatty acids and amino acids,dialkylsulfosuccinic acid ester salts, alkylsulfosuccinates,naphthenates, alkylether carboxylates, acylated peptides, α-olefinsulfonates, N-acrylmethyl taurine, alkylether sulfonates, secondaryhigher alcohol ethoxysulfates, polyoxyethylene alkylphenylethersulfates, monoglycylsulfates, alkylether phosphates and alkylphosphates, alkyl phosphonates and bisphosphonates, includedhydroxylated or aminated derivatives.

For example, polymers and copolymers of styrene sulfonate salts,unsubstituted and substituted naphthalene sulfonate salts (e.g. alkyl oralkoxy substituted naphthalene derivatives), aldehyde derivatives (suchas unsubstituted alkyl aldehyde derivatives including formaldehyde,acetaldehyde, propylaldehyde, and the like), maleic acid salts, andmixtures thereof may be used as the anionic dispersing aids.

Salts include, for example, Na+, Li+, K+, and substituted andunsubstituted ammonium cations. Representative examples of cationicsurfactants include aliphatic amines, quaternary ammonium salts,sulfonium salts, phosphonium salts, and the like.

U.S. Pat. Nos. 5,133,803 and 5,221,334 disclose the use of acetylenicdiol surfactants in aqueous, pigmented inkjet inks. The entire contentsof U.S. Pat. Nos. 5,133,803 and 5,221,334 are hereby incorporated byreference.

U.S. Pat. No. 8,052,269 discloses a combination of surfactantscomprising at least two of an ethoxylated nonionic fluorosurfactant, anonionic alcohol ethoxylate surfactant, and an anionic phosphatefluorosurfactant, provided that the combination of surfactants resultsin a foaming half-life of the inkjet ink which is less than 100 minutes.The entire content of U.S. Pat. No. 8,052,269 is hereby incorporated byreference.

U.S. Pat. No. 6,436,180 discloses the use of alkoxylatedfluorosurfactants in aqueous inkjet inks. The entire content of U.S.Pat. No. 6,436,180 is hereby incorporated by reference.

U.S. Pat. No. 9,487,666 discloses that the composition of Capstone eFS-3100 was a mixture of fluorosurfactants where x was always 6 and ywas in the range of 7 to 17 as well as 25 to 35. The entire content ofU.S. Pat. No. 9,487,666 is hereby incorporated by reference.

U.S. Pat. No. 5,852,075 describes the structural range of this class offluorinated surfactants and their usage in inkjet inks. The entirecontent of U.S. Pat. No. 5,852,075 is hereby incorporated by reference.

U.S. Pat. Nos. 6,444,017 and 9,783,692 disclose the use offluorosurfactants in aqueous inkjet inks. The entire contents of U.S.Pat. Nos. 6,444,017 and 9,783,692 are hereby incorporated by reference.

U.S. Pat. No. 9,783,692 describes the limited utility of Capstone eFS-3100 replacements for longer fluorocarbon chain surfactants. Asdisclosed by U.S. Pat. No. 9,783,692, various surfactant additives havebeen used previously in order to effectively wet low surface energymedia and control image quality defects, such as color-to-color bleedand area fill mottle. These additives are used in an attempt to providedesired wetting properties and to perform well in a high-speed thermalor piezo printhead.

Materials that have been used include nonionic fluorosurfactants withperfluorinated chains of C8 or larger, but these materials areincreasingly being replaced with short-chain analogs due to stewardshipconcerns (C6 or lower). One drawback of the short-chain materials isthat the lower hydrophobicity typically provides poorer wetting andimage quality control in inkjet printing than traditional longer-chainperfluorinated materials, and this ultimately limits the throughput ofhigh-speed inkjet printing.

Representative examples of nonionic dispersants or surfactants that canbe used in ink jet inks include fluorine derivatives, siliconederivatives, acrylic acid copolymers, polyoxyethylene alkyl ether,polyoxyethylene alkylphenyl ether, polyoxyethylene secondary alcoholether, polyoxyethylene styrol ether, ethoxylated acetylenic diols,polyoxyethylene lanolin derivatives, ethylene oxide derivatives ofalkylphenol formalin condensates, polyoxyethylene polyoxypropylene blockpolymers, fatty acid esters of polyoxyethylene polyoxypropylenealkylether polyoxyethylene compounds, ethylene glycol fatty acid estersof polyethylene oxide condensation type, fatty acid monoglycerides,fatty acid esters of polyglycerol, fatty acid esters of propyleneglycol, cane sugar fatty acid esters, fatty acid alkanol amide es,polyoxyethylene fatty acid amide es and polyoxyethylene alkylamineoxides.

The ink is comprised of an aqueous vehicle which is a mixture of waterand water-soluble organic solvents. The water is preferablyion-exchanged water (deionized water).

The water-soluble organic solvent may be contained in the ink usually inan amount ranging from 3% by weight to 50% by weight, preferably from 3%by weight to 40% by weight, of the total weight of the ink. The watermay be used in an amount ranging from 10% by weight to 90% by weight,and preferably from 30% by weight to 80% by weight, of the total weightof the ink.

The inks is preferable comprised of water, 2-pyrrolidone. Co-solventsare extensively used in aqueous inkjet inks to improve the solubility ofvarious other components, to affect the rate of drying, to act ashumectants to prevent ink drying in the printhead, as penetrants,buffers, and stabilizers.

The use of pyrrolidones as co-solvents in inkjet inks is well known; forexample, U.S. Pat. No. 3,846,141 discloses that the jet printing inkcomposition is formulated to include a solubilizing agent in order toensure that the water-soluble dye or dyes remain in solution in theaqueous vehicle. The solubilizing agent is N-methyl-Z-pyrrolidone,although a variety of other well-known equivalent solubilizing agentsincluding, for example, fi,/3-dihydroxyethyl sulfide (Kramefax-UnionCarbide), N-vinylpyrrolidone (boiling point 148° C.), substitutedpyrrolidone (Solvofen HM-GAF), 4 methoxy-4-methyl-pentanone-2 andtetrahydrofurfuryl alcohol. The entire content of U.S. Pat. No.3,846,141 is hereby incorporated by reference.

Japanese Patents JPH06668462, JP2714482 B2, JP251621862, and JP3147948B2and U.S. Pat. Nos. 4,694,302; 5,188,664; and 5,700,317 disclose the useof unsubstituted pyrrolidones and other co-solvents. The entire contentsof U.S. Pat. Nos. 4,694,302; 5,188,664; and 5,700,317 are herebyincorporated by reference.

The liquid vehicle comprises water and at least one organic solventpresent in an amount ranging from 1% to 50% relative to the total weightof the inkjet ink composition. The amount of the solvent can be varieddepending on a variety of factors, including the properties of thesolvent (solubility and/or dielectric constant), the type of colorant,and the desired performance of the resulting inkjet ink composition. Thesolvent preferable used ranges from 1% to 40% by weight based on thetotal weight of the inkjet ink composition, and more preferably from 1%to 30%.

Examples of suitable organic solvents include low molecular-weightglycols (such as ethylene glycol (boiling point 180° C.), diethyleneglycol, triethylene glycol, tetraethylene glycol, dipropylene glycol,ethylene glycol monomethyl ether, ethylene glycol monoethyl ether,triethylene glycol monomethyl or monoethyl ether, diethylene glycolmonomethyl ether, diethylene glycol monoethyl ether, diethylene glycolmonobutyl ether, and tetraethylene glycol monobutyl ether); alcohols(such as ethanol, propanol, iso-propyl alcohol, n-butyl alcohol (boilingpoint 118° C.), sec-butyl alcohol, and tert-butyl alcohol, 2-propyn-1-ol(propargyl alcohol), 2-buten-1-ol, 3-buten-2-ol, 3-butyn-2-ol, andcyclopropanol); diols containing from about 2 to about 40 carbon atoms(such as 1,3-pentanediol, 1,4-butanediol, 1,5-pentanediol,1,4-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 2,6-hexanediol,neopentylglycol (2,2-dimethyl-1,3-propanediol), 1,3-propanediol,1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2,6-hexanetriol, andpoly(ethylene-co-propylene) glycol, as well as their reaction productswith alkylene oxides, including ethylene oxides, including ethyleneoxide and propylene oxide); triols containing from about 3 to about 40carbon atoms (such as glycerine (glycerol), trimethylolethane,trimethylolpropane, 1,3,5-pentanetriol, 1,2,6-hexanetriol, and the likeas well as their reaction products with alkylene oxides, includingethylene oxide, propylene oxide, and mixtures thereof); polyols (such aspentaerythritol); amide es (such as dimethyl formaldehyde and dimethylacetamide e); ketones or ketoalcohols (such as acetone and diacetonealcohol); ethers (such as tetrahydrofuran and dioxane); lactams (such as2-pyrrolidone, N-methyl-2-pyrrolidone, and ε-caprolactam); ureas or ureaderivatives (such as di-(2-hydroxyethyl)-5,5,-dimethyl hydantoin(dantacol) and 1,3-dimethyl-2-imidazolidinone); inner salts (such asbetaine); and hydroxyamide e derivatives (such as acetylethanolamine,acetylpropanolamine, propylcarboxyethanolamine, and propylcarboxypropanolamine, as well as their reaction products with alkylene oxides).Additional examples include saccharides (such as maltitol, sorbitol,gluconolactone and maltose); sulfoxide derivatives (symmetric andasymmetric) containing from about 2 to about 40 carbon atoms (such asdimethylsulfoxide, methylethylsulfoxide, and alkylphenyl sulfoxides);and sulfone derivatives (symmetric and asymmetric) containing from about2 to about 40 carbon atoms (such as dimethylsulfone, methylethylsulfone,sulfolane (tetramethylenesulfone, a cyclic sulfone), dialkyl sulfones,alkyl phenyl sulfones, dimethylsulfone, methylethylsulfone,diethylsulfone, ethylpropylsulfone, methylphenylsulfone,methylsulfolane, and dimethylsulfolane). The organic solvent cancomprise mixtures of organic solvents.

In addition to the above components, a humectant may be optionally addedto the ink in order to give an ink having the desired values of physicalproperties.

Various colorants useful in inkjet inks are disclosed in U.S. Pat. No.8,287,112. The entire content of U.S. Pat. No. 8,287,112 is herebyincorporated by reference.

Colorants used in the inkjet inks may be pigments, dyes or a combinationthereof.

The term “dye”, as used herein, means an oleophilic colorant having asolubility of 10 mg/L or more in the dispersed phase in which it isapplied and under the ambient conditions pertaining.

Pigments may be used in the inkjet ink. The inkjet ink preferablycontains an organic and/or inorganic pigment as colorant. If thecolorant is not a self-dispersible pigment, the inkjet ink preferablyalso contains a dispersant, more preferably a polymeric dispersant.

Pigments may be dispersed in the aqueous vehicle by dispersing agents,such as polymeric dispersants or surfactants. Additionally, the surfaceof the pigments can be modified to obtain so-called “self-dispersible”or “self-dispersing” pigments, i.e. pigments that are dispersible in thedispersion medium without dispersants.

The pigments in the aqueous inkjet inks may be black, white, cyan,magenta, yellow, red, orange, violet, blue, green, brown, mixturesthereof, and the like. The color pigment may be chosen from thosedisclosed by HERBST, Willy, et al. Industrial Organic Pigments,Production, Properties, and Applications. 3rd edition. Wiley-VCH, 2004.ISBN 3527305769.

Preferred pigments are C.I. Pigment Yellow 1, 3, 10, 12, 13, 14, 17, 55,65, 73, 74, 75, 83, 93, 97, 109, 111, 120, 128, 138, 139, 150, 151, 154,155, 180, 185 and 213. More preferably, yellow pigments are C.I. PigmentYellow 74, 128, 139, 150 155 and 213. Preferred pigments are C.I.Pigment Red 17, 22, 23, 41, 48:1, 48:2, 49:1, 49:2, 52:1, 57:1, 81:1,81:3, 88, 112, 122, 144, 146, 149, 169, 170, 175, 176, 184, 185, 188,202, 206, 207, 210, 216, 221, 248, 251, 254, 255, 264, 270 and 272.Preferred pigments are C.I. Pigment Violet 1, 2, 19, 23, 32, 37, and 39.Preferred pigments are C.I. Pigment Blue 15:1, 15:2, 15:3, 15:4, 15:6,16, 56, 61, and (bridged) aluminum phthalocyanine pigments. Preferredpigments are C.I. Pigment Orange 5, 13, 16, 34, 40, 43, 59, 66, 67, 69,71, and 73.

Preferred pigments are C.I. Pigment Green 7 and 36. Preferred pigmentsare C.I. Pigment Brown 6 and 7. Suitable pigments include mixed crystalsof the above particular preferred pigments. A commercially availableexample is Cinquasia Magenta RT-355-D from Ciba Specialty Chemicals.

Carbon black is preferred as a pigment for the black inkjet ink.Suitable black pigment materials include carbon blacks such as PigmentBlack 7 (e.g. Carbon Black MA80 from MITSUBISHI CHEMICAL), REGAL® 400R,MOGUL® L, ELFTEX® 320 from CABOT Co., or Carbon Black FW18, SpecialBlack 250, Special Black 350, Special Black 550, PRINTEX® 25, PRINTEX®36, PRINTEX® 55, PRINTEX® 90, PRINTEX® 150T from DEGUSSA.

Additional examples of suitable pigments are disclosed in U.S. Pat. No.5,389,133. Particular preferred pigments are C.I. Pigment White 1, 2, 3,4, 5, 6, 7, 10, 11, 12, 14, 17, 18, 19, 21, 24, 25, 27, 28, and 32. Theentire content of U.S. Pat. No. 5,389,133 is hereby incorporated byreference.

It is also possible to make mixtures of pigments in the color inkjetinks. For some applications, a neutral black inkjet ink is preferred andcan be obtained, for example, by mixing a black pigment and a cyanpigment into the ink. Also non-organic pigments may be present in thecolor inkjet inks. Particularly preferred pigments Illustrative examplesof the inorganic pigments include red iron oxide (III), cadmium red,ultramarine blue, Prussian blue, chromium oxide green, cobalt green,amber, titanium black and synthetic iron black.

Specific examples of commercially available pigment dispersions includePro-Jet Cyan APD1000, Pro-Jet Magenta APD1000, Pro-Jet Yellow APD1000,Pro-Jet Yellow (LF) APD1000, Pro-Jet Black APD1000 from Fujifilm ImagingColorants, Inc., Cab-O-Jet 200 black, Cab-O-Jet 250C cyan, Cab-O-Jet260M magenta, Cab-O-Jet 265M magenta, Cab-O-Jet 270 yellow, Cab-O-Jet300 black, Cab-O-Jet 352 black, Cab-O-Jet 400 black, Cab-O-Jet 450Ccyan, Cab-O-Jet 465M magenta, Cab-O-Jet 470Y yellow, Cab-O-Jet 480Vviolet, Cab-O-Jet 554B blue, Cab-O-Jet 740Y yellow, from CabotCorporation, Specialty Cyan Dispersion Type A1, Specialty CyanDispersion Type A1, Specialty Cyan Dispersion Type A1, Specialty CyanDispersion Type P1, Specialty Cyan Dispersion Type P2, Specialty MagentaDispersion Type A1, Specialty Magenta Dispersion Type A2, SpecialtyMagenta Dispersion Type A3, Specialty Magenta Dispersion Type P1,Specialty Magenta Dispersion Type P3, Specialty Yellow Dispersion TypeA1, Specialty Yellow Dispersion Type A2, Specialty Yellow DispersionType P1, Specialty Yellow Dispersion Type P2, Specialty Black DispersionType A1, Specialty Black Dispersion Type P2, Specialty Black DispersionType P4, Specialty Black Dispersion Type SD2, Specialty Black DispersionType SD4, Specialty Red Dispersion Type P1, Specialty Green DispersionType P1, Specialty Green Dispersion Type P2, Specialty Green DispersionType P3, Specialty Green Dispersion Type P4, Specialty Orange DispersionType P1, Specialty Violet Dispersion Type P1, Specialty White DispersionType P1, from Eastman Kodak™ Company, Mega Cyan, Mega Magenta, MegaYellow 2, Mega Black, DU 1010 cyan, DU 1020 magenta, DU 1030 yellow, DU1031 yellow, DU 1040 black, DU 1041 black, from E. I. du Pont de Nemoursand Company Cylcojet Blue 15:3 Liquid, Cylcojet Blue 15:3 Liquid,Cylcojet Blue 15:3 Liquid, Cylcojet Blue 15:0 & 15:4 Liquid, CylcojetBlue 60 Liquid, Cylcojet Brown 25 Liquid, Cylcojet Red 122 Liquid BlueShade, Cylcojet Red 122 Liquid Yellow Shade, Cylcojet Black 7 Liquid,Cylcojet Violet 19 Liquid Blue Shade, Cylcojet Violet 19 Liquid YellowShade, Cylcojet Yellow 74 & 155 Liquid, Cylcojet Orange 34 & 43,Cylcojet White 6 Liquid, from Lever Colors, Inc., Hostajet Yellow 4G-PTVP2669, Hostajet Red D3G-PT VP 5152, Hostajet Magenta E5B-PT VP3565,Hostajet Magenta E7B-PT VP 5122, Hostajet Magenta E-PT, Hostajet CyanBG-PT, Hostajet Green 8G-PT VP 5154, Hostajet Black O-PT, from ClariantInternational, Ltd.

Pigment particles in inkjet ink should be sufficiently small to permitfree flow of the ink through the inkjet-printing device, especially atthe ejecting nozzles. It is also desirable to use small particles formaximum color strength and to slow down sedimentation.

When measured by a laser diffraction particle sizing apparatus such asthe Horiba LA-950 and the like, the volume average pigment particle sizeof a dispersed non-white pigment is preferably between 0.020 and 1 μm,more preferably between 0.040 and 0.200 μm and particularly preferablybetween 0.050 and 0.150 μm. Most preferably, the numeric average pigmentparticle size is no larger than 0.100 μm. For the white pigmentdispersion when measured by a laser diffraction particle sizingapparatus such as the Horiba LA-950 and the like, the volume averagepigment particle size of the white pigment is preferably from 50 to 500nm, more preferably from 150 to 400 nm, and most preferably from 200 to350 nm. Sufficient hiding power cannot be obtained when the averagediameter is less than 50 nm, and the storage ability and the jet-outsuitability of the ink tend to be degraded when the average diameterexceeds 500 nm.

The pigment is preferably used in the pigment dispersion used forpreparing the inkjet inks in an amount of 10 to 40 wt %, preferably 12to 30 wt % based on the total weight of the pigment dispersion. In theinkjet ink the pigment is preferably used in an amount of 0.1 to 20 wt%, preferably 0.5 to 10 wt % based on the total weight of the inkjetink.

The ink composition optionally contain one or more other ingredients,such as, buffering/neutralizing agents, adhesion promoters,bactericides, fungicides, algicides, sequestering agents, softeners,thickeners, anti-foaming agents, anti-kogation agents, corrosioninhibitors, light stabilizers, anti-curl agents, thickeners,non-reactive agents, softeners/plasticizers, specialized dispersingagents, specialized Surface active agents, conductivity agents(ionizable materials) and/or other additives and adjuvants well-known inthe relevant art.

pH adjusting agents include, inorganic and organic water soluble acidsand inorganic and water soluble bases, and amphoteric compounds.Non-limiting examples include sodium hydroxide, potassium hydroxide,ammonium hydroxide, primary, secondary, and tertiary amines such astriethanolamine (TEA), triethyamine, dimethyl ethanolamine (boilingpoint 134° C.), 2-amino-2-methyl-1-propanol, amino acids such astris(hydroxymethyl amino methane), hydrochloric acid, sulfuric acid,phosphoric acid, nitric acid, acetic acid, propionic acid, and the like.pH adjusting agents may also function as cosolvents in the ink vehicle

Non-limiting examples of anti-foaming agents (defoamer) include BYK 024,BYK 012: BYK 31 (commercially available from Byk-Chemie), FOAMEX 810,AIREX 901, AIREX 902 (commercially available from Evonik Tego ChemieGmbH, Essen, Germany), SURFYNOL DF 37, SURFYNOL DF 210, SURFYNOL DF 75(commercially available from Air Products Ltd.), and the like.

Inkjet inks contain Proxel GXL, a broad spectrum biocide to protectthese inks from spoilage from by bacteria, yeasts, and fungi. Proxel GXLis 1,2-benzisothiazolin-3-one and is well known to those skilled in theart as an effective preservative for thermal inkjet inks, see forexample U.S. Pat. No. 5,188,664.

For thermal inkjet inks, a long chain phosphate ester may beincorporated in the ink as an anti-kogation additive. U.S. Pat. No.5,062,892 discloses kogation as a build-up of ink components on theheater (resistor) in the thermal inkjet print head and the use ofphosphates to moderate the impact of such buildup. The entire content ofU.S. Pat. No. 5,062,892 is hereby incorporated by reference.

Without subscribing to any particular theory, it appears that thekogation effect is due to adsorption of dye and/or decompositionproducts of ink on the resistor surface. The appearance and increase inadsorbed dye or decomposition products apparently reduces the volume ofink fired. The additive is believed to eliminate or reduce theadsorption process.

U.S. Pat. No. 5,062,892 further discloses that the most effectiveanti-kogation additives are phosphate salts; added either as dibasic(HPO4 2-) monobasic (H2 PO4-), polyphosphates such as diphosphate (P2 074-), or phosphate esters.

The use of long chain phosphate esters is disclosed in European PatentNumber 084804561 and U.S. Pat. No. 6,610,129. The entire content of U.S.Pat. No. 6,610,129 is hereby incorporated by reference.

U.S. Pat. No. 9,587,130 discloses the use of Oleth-3 phosphate esters ininkjet inks. The entire content of U.S. Pat. No. 9,587,130 is herebyincorporated by reference.

The inkjet ink is comprised of electrophilic crosslinking agents.Examples of electrophilic crosslinking agents include p-hydroxyalkyamide yl crosslinkers and other related compounds.

U.S. Pat. No. 6,341,856 discloses several electrophilic crosslinkinggroups capable of reacting with active hydrogen. Such reactive groupsinclude isocyanate; epoxy; carboxylic acid and derivatives;organometallic crosslinking agents such as the organic chelates oftitanium, aluminum, zinc, zircon or chromium; and silane couplingagents. The entire content of U.S. Pat. No. 6,341,856 is herebyincorporated by reference.

European Patent 1,853,43161 discloses several electrophilic crosslinkingagents including carbodiimide and polycarbodiimide, triazine andaminotriazine such as methoxymethyl melamine cross-linking agent,aziridine and polyfunctional azridine, polyacrylamide e,acetoacetoxy-functional polymeric crosslinking agent, melamine resinssuch as trimethoxymethylmelamine (TMMM), hexamethoxymethylmelamine(HMMM) or other modified melamine resins such as acrylated melamine,benzoguanamine, urea crosslinking resins, reactive silane. The entirecontent of European Patent 1,853,43161 is hereby incorporated byreference.

Deprotinated acrylic acid polymers and their salts act as neucophiles inthe reaction with electrophilic crosslinking agents. Neucophiliccrosslinking agents, such as hydrazides for example, have poorreactivity with such neucophilic polymers.

EXAMPLES

The following examples illustrate a number of embodiments of the presentinvention that are presently known. However, it is to be understood thatthe following are only exemplary or illustrative of the application ofthe principles of the present invention. Numerous modifications andalternative compositions, methods, and systems may be devised by thoseskilled in the art without departing from the spirit and scope of thepresent invention. The appended claims are intended to cover suchmodifications and arrangements. Thus, while the present invention hasbeen described above with particularity, the following examples providefurther detail in connection with what are presently deemed to be theacceptable embodiments.

Exemplary aqueous inkjet inks are prepared comprising aqueous inkvehicle with at least one water soluble organic solvent, a pigmentdispersion, a copolymer comprising carboxylic acid groups dissolved inthe vehicle wherein the carboxylic acid groups are base neutralized anda water stabilized poly-electrophilic functionalized compound capable ofcrosslinking the neutralized carboxylic acidic groups on the copolymer.

Some of the following examples were tested for operability in a thermalink-jet printer, such as a HP™ Officejet Pro 8000™. 20 g of each ink wascharged into an ink cartridge. The filled cartridge was then insertedinto the HP™ Officejet Pro8000™ and 60 pages were printed in blocks ofsolid color to clear the previous ink from the lines and printhead ofthe printer. With each of the exemplified inks, blocks were continuouslyprinted until a significant loss of nozzles was noted.

Some of the following examples were tested for operability in a piezoink-jet printer, such as an Epson StylusC88+™. 20 g of each ink wascharged into an ink cartridge. The filled cartridge was then insertedinto the Epson Stylus C88+™ and multiple pages were printed. With eachof the exemplified inks, blocks were continuously printed until asignificant loss of nozzles was noted.

Some ink samples were measured for pH, viscosity, dynamic surfacetension, static surface tension, and/or particle size. Samples weremeasured fresh and after aging in sealed containers for up to 6 weeks at60° C. to assess their stability.

The rub durability performance of the following examples was assessed inorder to evaluate the resistance of dried ink samples on a substrate toabrasion and chemical damage. Ink examples were drawn down onto glossyvinyl substrates (HP™ Permanent Gloss Adhesive Vinyl (J3H62A)) and driedfor up to 96 hours at 60° C. The dried ink drawdowns were measured fordry rub durability as well as wet rub durability with water, a spraycleaner (Windex™ Ammonia Free by SC Johnson™) and isopropanol (100%).

Rub durability testing was conducted on the examples using a Taber™Crockmeter. For the dry rub test, a dried ink drawdown example wasplaced in a Crockmeter equipped with a crock-cloth covered tip. The armweight on the Crockmeter was measured at 1,428 g, an additional 928 gweight was place on the arm directly over the tip. The Crockmeter wasturned ON and the crock-cloth tip moved in a linear motion back andforth for 100 cycles. The sample was removed and visually ranked on ascale of 0 to 10 for abrasion damage. Compared to un-rubbed samples, therub resistance of an example was rated as excellent (▪), with little orno visual damage, a ranking of 8 to 10. Examples were rated as very good(□), with slight visual damage, a ranking of 6 to 8. Examples were asgood (●), with visual damage, a ranking of 4 to 6. Examples were ratedas fair (∘), with modest visual damage, a ranking of 2 to 4. Exampleswere rated as poor (x), with severe visual damage, a ranking of 0 to 2.

Wet rub durability testing was also conducted on the samples in asimilar fashion. For wet water rub durability, 0.5 cc of water wasplaced on the sample and the crock-cloth covered tip placed in thewater. The Crockmeter was then turned ON for 100 cycles.

For wet window cleaner rub durability, 0.5 cc of Windex™ was placed onthe sample and the crock cloth covered tip placed in the liquid. TheCrockmeter was then turned on for 30 cycles.

For wet isopropanol rub durability, 0.5 cc of isopropanol (100%) wasplaced on the sample and the crock-cloth covered tip placed in theliquid. The Crockmeter was then turned ON for 30 cycles.

Ink examples were measure for viscosity in the fresh state as well asafter ink aging in a sealed glass container for up to 6 weeks at 60° C.Viscosity measurements were made using a Brookfield DV-E viscometer in awater bath controlled to 20° C.

Some ink examples were measured for particle size distribution (PSD)using a Horiba LA-950 V2 Laser Scattering Particle Size DistributionAnalyzer. This device uses the principles of Mie and Fraunhoferscattering theory to calculate the size and distribution of particlessuspended in a liquid. The measured particle size range is 0.01 to 3000μm for LA950V2. The application of this method to pigmented aqueousinkjet inks has been developed using the flow cell method.

In this method the refractive index of the pigment dispersion containedin the ink example is entered into the instrument and the flow cell isprepared for measurement by circulating (reverse osmosis and de-ionized)RODI water through the Vortex Genie for 30 seconds to ensure that therewas no residue in the apparatus. 180 mL DI water is then added to theinstrument and analyzed as a blank sample.

Example inks were characterized for PSD by using a disposablemicropipette to dispense sufficient ink into the 180 ml of RODI water inthe Vortex Genie and flow cell until the light transmittance of theinstrument dropped to 60%. This typically required about 320 μL of ink.PSD measurements are reported as 50th percentile fraction (D50) below agiven particle size (μm).

Ink examples 1 to 14 are shown in Table 1 of FIG. 1 and ink examples 15to 28 are shown in Table 2 of FIG. 2. These examples were prepared inthe following fashion.

A stock solution of a carboxylated styrene-acrylate copolymer resin(Joncryl 683) in basic pH solution was prepared. The Joncryl 683 resinused had a Tg of 75° C. and an acid number of 165 mg KOH/g. First, 4 gof KOH was dissolved into 76 g of RODI water. 20 g of the solid resinwas added to the basic solution and stirred under ambient conditionsuntil fully dissolved into solution, about 12 hours.

50 g of each ink example was prepared by adding the make-up RODI watercalled for in each example, typically about 59 g, to a 100 cc Pyrexbeaker. A magnetic stir bar was added to the beaker and the waterstirred with modest agitation. To the RODI water was added the amountand type of biocide, humectant, and surfactant called for in eachexample. 10 g of the resin stock solution was then thoroughly mixed intothe ink. The crosslinker was then added to the ink and stirred for 30minutes. Finally, 12 g of Specialty Black A1 pigment dispersion(supplied by Eastman Kodak™ Co.) was thoroughly mixed into the ink. Theink was then filtered through a 1 micron disk filter.

Ink examples 1 to 14 of Table 1 of FIG. 1 were prepared with glyceroland 2-Pyrrolidone water miscible solvents (humectants), surfactantsincluding Surfynol 440 (supplied by Evonik) and Capstone e FS-31(supplied by Chempoint). Proxel GXL (supplied by Lonza) was the biocide.The following electrophilic crosslinkers were utilized: Primid XL-552 abeta hydroxy amide crosslinker supplied by Estron Chemical, EpocrosWS-700 Oxazoline functionalized reactive copolymer crosslinker suppliedby NIPPON SHOKUBAI CO., LTD, Cymel 303 LF highly methylated, monomericmelamine crosslinker supplied by Allnex USA Inc., Carbodolite V-02-L2and Carbodolite V-04 Polycarbodiimide crosslinkers supplied by NisshinboChemical Inc., Denacol EX-321 multifunctional type aliphatic epoxycrosslinker supplied by Nagase and Co., LTD., CX-100 polyfunctionalaziridine liquid crosslinker supplied by DSM Coating Resins, LLC, EMTechCL-100 (supplied by Target Coatings, Inc.), Ammonium Zirconium (IV)Carbonate solution crosslinker supplied by Sigma-Aldrich, Tyzor LAorganic titinate crosslinker supplied by Dorf Ketal Chemicals, LLC,Zoldine XL-29SE polymeric carbodiimide crosslinking agent supplied byAngus Chemical Co., Flexipol MKO-20 blocked isocyanate crosslinkingagent supplied by Innovative Chemical Technologies, Inc. The followingnucleophilic crosslinker was utilized: Adipic Dihydrazide (supplied bySigma-Aldrich).

For example, example ink 3 of Table 1 of FIG. 1 was prepared bycombining 12 g of Kodak™ Specialty Black A1 dispersion, 10 g of Joncryl683 resin stock solution, 6 g of glycerol, 12 g of 2-pyrrolidone, 0.3 gof Surfynol 440, 0.3 g of Capstone FS-31, 0.2 g of Proxel GXL and 3.03 gof Epocros WS-700.

Ink examples 15 to 28 of Table 2 of FIG. 2 were prepared in anequivalent fashion to examples 1 to 14 with the exception that ethyleneglycol was substituted for glycerol.

For example, example ink 17 of Table 2 of FIG. 2 was prepared bycombining 12 g of Kodak™ Specialty Black A1 dispersion, 10 g of Joncryl683 resin stock solution, 6 g of 2-pyrrolidone, 12 g of ethylene glycol,0.3 g of Surfynol 440, 0.3 g of Capstone FS-31, 0.2 g of Proxel GXL and3.03 g of Epocros WS-700.

As illustrated by Tables 3, 4, and 5 of FIGS. 3 through 5, respectively,the dry rub durability of Example inks 3, 4, 6, 17, 18, and 20 have beencompared with control Example inks 1 and 15. Example inks 1, 3, 4, and 6were prepared in ink vehicle 1 containing high boiling humectants whichmake these inks examples slower to dry, cure and develop durability.Example inks 15, 17, 18, and 20 were prepared in ink vehicle 2containing low boiling humectants which make these inks faster to dry,cure and develop durability. As illustrated by Tables 3, 4, and 5 ofFIGS. 3 through 5, respectively, control Example inks 1 and 15, each ofwhich do not contain electrophilic crosslinkers, do not develop dry rubdurability, even after 96 hours at 60° C.

For example, as illustrated by Table 3 of FIG. 3, Example ink 3,prepared in ink vehicle 1 with 3.3% of the electrophilic crosslinkerEpocros WS-700 was evaluated for dry rub durability as a function ofdrying time at 60° C. Without any added triethanolamine (TEA), Exampleink 3 was rated as Poor (x) after 24 hours drying, as Fair (∘) after 48hours drying, as Very Good (□) after 72 hours drying and as Excellent(▪) after 96 hours drying.

Example inks 3 and 17 were prepared with the Epocros WS-700 crosslinkerand develop good dry rub durability after 42 to 78 hours at 60° C.,depending upon the ink vehicle. However, when tertiary amine stabilizerswere added to these inks (0.5-2% triethanol amine), these ink neverdeveloped an excellent level of durability and were much slower todevelop good levels of durability, particularly in slower drying Vehicle1.

Example inks 4 and 18 were prepared with the Cymel 303 LF crosslinkerand develop good dry rub durability after 42 to 78 hours at 60° C.,depending upon the ink vehicle. However, when tertiary amine stabilizersare added to these inks (0.5-2% triethanol amine), these ink Examplesonly developed a fair level of durability.

Example inks 6 and 20 were prepared with the Carbodolite V-04crosslinker and develop good dry rub durability after 42 to 78 hours at60° C., depending upon the ink vehicle. However, when tertiary aminestabilizers were added to these inks (0.5-2% triethanol amine), theseink were slower to develop good levels of durability and in some casesnever developed excellent levels of durability.

The wet and dry rub durability of Example inks 2-14 and 16-28 were goodto excellent after drying for 78 hours at 60° C.

The dry and wet rub chemical durability of Example inks 2-14 arecompared with control Example ink 1, as shown in Tables 6, 7, 8, and 9of FIGS. 6 through 9, respectively. As demonstrated in Tables 6, 7, 8,and 9 of FIGS. 6 through 9, respectively, all Example inks develop fairto excellent wet rub chemical durability to water, widow cleaner, andisopropanol after drying and curing for 96 hours at 60° C.

For example, Example ink 5 was evaluated for rub durability after beingdrawn down onto a glossy vinyl substrate and dried for 72 hours at 60°C. Example ink 5 was rated a Good (●) for dry rub (Table 6 of FIG. 6),Very Good (□) for wet (water) rub (Table 7 of FIG. 7), Good (●) forwindow cleaner rub (Table 8 of FIG. 8), and Poor (x) for isopropylalcohol rub (Table 9 of FIG. 9).

Example ink 8, containing the nucleophilic crosslinking agent adipicdihydrazide, shows the over-all lowest level of durability compared tothe other electrophilic crosslinking agents.

As noted above, the wet isopropanol rub chemical durability of Exampleinks 2-14 are compared with control Example ink 1, as shown in Table 9of FIG. 9. As demonstrated in Table 9, all Example inks develop fair wetrub chemical durability to isopropanol after drying and curing for 72hours at 60° C. When tertiary amines were added to the ink, theresistance to isopropanol rubbing generally decrease, regardless ofwhether triethanol amine or triethyl amine were added in at the 1%level.

For example, Example ink 10 was evaluated for isopropyl alcohol rubresistance after being drawn down onto a glossy vinyl substrate anddried for 72 hours at 60° C. With no added tertiary amine, Example ink10 was rated as Excellent (▪) for isopropyl alcohol rub resistance; with1% triethanol amine, Example ink 10 was rated as very good (□); and with1% triethyl amine, Example ink 10 was rated as good (●).

Example inks 1-14, as shown in Table 10 of FIG. 10, were assessed forstability by measuring the change in viscosity. Freshly prepared inkexamples were compared to examples aged for 6 weeks at 60° C. in sealedglass containers. The viscosity of fresh ink examples varied from 2.5 cPto 3.5 cP. Changes in viscosity over the keeping period were judgedexcellent if less than 0.06 cP, very good if between 0.06 and 0.15 cP,good if between 0.15 and 0.3 cP, fair if between 0.3 and 0.6 cP, andpoor if greater than 0.6 cP.

For example, Example ink 4 was evaluated for changes in viscosity afterconditioning the ink sample for 8 weeks at 60° C. With 0% addedtriethanol amine (TEA), the ink stability was rated as Excellent (<0.06cP) as the ink increase in viscosity after conditioning by 0.03 cP; with0.5% added TEA, the ink stability was rated as Good (0.15 to 0.30 cP) asthe ink increase in viscosity after conditioning by 0.17 cP; and with2.0% added TEA, the ink stability was rated as Fair (0.30 to 0.60 cP) asthe ink increase in viscosity after conditioning by 0.35 cP.

Example inks 6, 13 and 14 gelled or solidified during the keepingperiod. Unexpectedly, the addition of tertiary amine stabilizers did notstabilize the example inks from crosslinking during the keepingcondition. In fact, the addition of 0.5% to 2% triethanol amine to theink examples actually degraded the ink stability of several of theexamples.

Not wishing to be bound to any particular theory, tertiary amines mayactually catalyze the reaction between electrophilic crosslinkers andcarboxy containing polymers.

Example inks 1-14, as shown in Table 11 of FIG. 11, were assessed forstability by measuring the change in their pigment dispersion particlesize. Freshly prepared ink examples were compared to examples aged for 6weeks at 60° C. in sealed glass containers. The pigment dispersionparticle size of fresh ink examples varied from 56 to 83 nm.

Increases in pigment dispersion particle size over the keeping periodwere judged excellent if less than 10 nm, very good if between 10 and 20nm, good if between 20 and 50 nm, fair if between 50 and 100 nm, andpoor if greater than 100 nm.

For example, Example ink 4 was measured for PSD after 8 weeksconditioning at 60° C. With 0% added triethanol amine (TEA), the inkstability was judged to be excellent (<10 nm) as the average PSDincreased by 8 nm; with 0.5% TEA, the ink stability was judged to begood (20-50 nm) as the average PSD increased by 22 nm; and with 2% addedTEA, the ink stability was judged to be fair (50-200 nm) as the averagePSD increased by 66 nm. Examples which gelled (solidified) could not bemeasured for PSD change.

Example inks 6, 13 and 14 gelled or solidified during the keepingperiod. Unexpectedly, the addition of tertiary amine stabilizers did notstabilize the example inks from crosslinking during the keepingcondition. In fact, the addition of 0.5% to 2% triethanol amine to theink examples actually degraded the ink stability of Example inks 3 and9.

Not wishing to be bound to any particular theory, tertiary amines mayactually catalyze the reaction between electrophilic crosslinkers andcarboxy containing polymers.

Example inks 9, 11 and 12, in Table 11, show significant increases inthe pigment PSD with ink keeping at 60° C. for 8 weeks. In the course ofmaking such PSD measurements it was noted that bi or tri modal particlesize distribution was present. Measurements of PSD were made in a highlydiluted state and it was observed that the larger particle size peaks inthe distribution would revert back to the original (fresh) mono-modalPSD.

Table 12 of FIG. 12 shows PSD data as a function of time for 8 week/60°C. aged Example inks 11 and 12, with and without 2% triethanol amineadded. Table 13 of FIG. 13 shows PSD data as a function of time for 8week/60° C. aged Example inks 13 and 7, with and without 2% triethanolamine added.

For example, Table 12 shows that Example ink 11, with 0% addedtriethanol amine (TEA), was measured for PSD after 8 weeks conditioningat 60° C. At time 0, a large PSD peak was observed at 6.2 microns whichaccounted for 55% of the scattering particles in the total PSD.

In the unaged state, Example 11 had an average PSD of 72 nm (0 TEA) and75 nm (2% TEA). After aging Example 11 ink for 8 week/60° C., 55% of thepigment dispersion aggregated into a 6.5 micron PSD mode (0% TEA) and19% into a 3 micron PSD mode (2% TEA).

However, as shown in Table 12, the larger PSD modes de-aggregated withtime back to the original (unaged) PSD. The size of the larger PSD modeand the rate of de-aggregation were both impacted by the presence oftriethanol amine in Example inks 11 and 12.

Unexpectedly, the data in Tables 12 and 13 shows the impact of waterstabilization on the reaction of electrophilic crosslinking agent withcarboxylated polymers in the inks of this invention. In the nominalwater concentration of the inks, the reactivity of some electrophiliccrosslinkers is sufficiently high with carboxylated binders to formmacro molecules which both increase the viscosity and aggregate thepigment dispersion upon aging at 8 week/60° C. After the 562x dilutionin the cell of the particle size analyzer, the equilibrium of the agedink shifts back to the original PSD of the Pigment dispersion due to thehuge increase in water concentration.

It was observed in this example that the presence of tertiary aminesdoes not stabilize the reaction of crosslinkers with carboxylatedpolymers.

Not wishing to be bound any particular theory, tertiary amines act ascatalysts in the water stabilized crosslinking reaction.

This unexpected water stabilization of pigmented ink containingelectrophilic crosslinkers and carboxylated polymers creates inks withlong term storage stability, excellent inkjet print head compatibility,and good outdoor durability after printing and drying. Such crosslinkingreactions do not require the addition of an inhibitor since thecrosslinking mechanisms are equilibrium based and dependent upon theconcentrations of the reactants and water.

The high water (or other protic solvent) content of the ink vehicleshifts the equilibrium of the reaction away from crosslinking reactions.After printing and drying of the ink onto media, the water (or otherprotic solvents) concentration is greatly reduced, thereby allowing theequilibrium to shift towards reaction of the crosslinker andcarboxylated polymers, resulting in the formation of high molecularweight crosslinked resins which encapsulates and bonds the pigmentparticles to the surface of the substrate.

While the crosslinked groups between polymer chains in the printed anddried ink may be reversible by hydrolysis, surprisingly, it has beenfound that such printed and dried inks have good resistance to water.

Not wishing to be bound to any particular theory, it is believed thatthe hydrophobic portions of such crosslinked polymers concentrate on thesurface of the printed and dried ink, creating a barrier to waterpenetration.

With the selection of less reactive electrophilic crosslinkers, inks maybe formulated having stable viscosity and dispersion PSD, even afterstorage at temperatures up to 60° C. for 6 weeks. After printing anddrying, water is removed from these inks, allowing the crosslinkingreaction to proceed and causing the carboxylated polymers to crosslinkand to develop high water resistance, thereby providing additionaldurability to the printed image without compromising the shelf-life ofthe ink.

Additionally, such electrophilic crosslinker containing inks, stabilizedby water, show good compatibility with thermal inkjet print heads.

Example inks 29 to 37 are shown in Table 14 of FIG. 14. These inkexamples were prepared in an equivalent fashion to Example inks 15 to 28with the exception that the potassium hydroxide neutralized carboxylatedstyrene acrylate polymer, Joncryl 683, was replaced with several ammonianeutralized carboxylated polymers.

Stock solutions of each of the carboxylated copolymer resins in Exampleinks 29-37 were in an equivalent fashion to the stock solution preparedin Example inks 1-28 with the exception that ammonia was substituted forthe potassium hydroxide added to the water to dissolve each solid resinunder ambient conditions.

For each resin stock solution, the pH was 8.9. No additional ammoniumhydroxide was required for Example ink 31 as the carboxylated resin wassuppled in a basic solution of water and ammonia.

For example, Example ink 29 was prepared by combining 12 g of Kodak™Specialty Black A1 dispersion, 10 g of resin stock solution (containing2 g of Joncryl 683, 0.73 g ammonia and the balance water) with 6 g of2-pyrrolidone, 12 g of ethylene glycol, 0.3 g of Surfynol 440, 0.3 g ofCapstone FS-31, 0.2 g of Proxel GXL and 3.03 g of Epocros WS-700.

The durability assessment of Example inks 29-35 are summarized in Table15 of FIG. 15. Rub durability testing was conducted on the example inksusing a Taber Crockmeter.

For the wet (H2O) and dry rub test, a dried ink drawdown example wasplaced in a Crockmeter equipped with a crock-cloth covered tip. The armweight on the Crockmeter was measured at 1,428 g; an additional 2010 gweight was place on the arm directly over the tip. The Crockmeter wasturned ON, and the crock-cloth tip moved in a linear motion back andforth for 1600 cycles.

For the window cleaner rub test, the arm weight on the Crockmeter wasmeasured at 1,428 g; an additional 920 g weight was place on the armdirectly over the tip. The Crockmeter was turned ON, and the crock-clothtip moved in a linear motion back and forth for 800 cycles.

For the isopropanol rub test, a dried ink drawdown example was placed ina Crockmeter equipped with crock-cloth covered tip. The arm weight onthe Crockmeter was measured at 1,428 g; an additional 920 g weight wasplace on the arm directly over the tip. The Crockmeter was turned ON,and the crock-cloth tip moved in a linear motion back and forth for 1200cycles.

Samples were removed and visually ranked on a scale of 0 to 10 forabrasion damage. Compared to un-rubbed samples, the rub resistance of anexample was rated as excellent (▪), with little or no visual damage, aranking of 8 to 10. Examples were rated as very good (□), with slightvisual damage, a ranking of 6 to 8. Examples were as good (●), withvisual damage, a ranking of 4 to 6. Examples were rated as fair (∘),with modest visual damage, a ranking of 2 to 4. Examples were rated aspoor (x), with severe visual damage, a ranking of 0 to 2.

For example, Example ink 29 was evaluated for rub durability. Thisexample was excellent for dry and water rub resistance and very good forwindow cleaner and isopropyl alcohol rub resistance.

The data shows that carboxylated resins of varying Tg, acid number, andmolecular weight may be employed to achieve good levels of durabilityafter printing a drying.

Example inks 38 to 49 are shown in Table 16 of FIG. 16. These inkexamples were prepared in an equivalent fashion to Example inks 15 to28.

For example, Example ink 39 was prepared by combining 10 g of Joncryl683 stock solution with 6 g of glycerol, 12 g of 2-pyrrolidone, 0.3 g ofSurfynol 440, 0.3 g of Capstone FS-31, 3 g of Proxel GXL and 13 g ofPrimid XL-552.

The ink stability of Example inks 38 to 49 are shown in Table 17 of FIG.17. More specifically, Table 17 of FIG. 17 shows the stability ofvarious electrophilic crosslinking agents with carboxyl containingpolymers at an equivalency ratio of 1:1. These examples were prepared ina similar fashion to Examples 1-14 with the exception that no pigmentdispersion was included. Exclusion of the pigment dispersions from theseexamples allowed the interaction of the crosslinker with thecarboxylated resin to be studied directly using light scatteringmeasurements. At high equivalency ratios, crosslinking reactions may befavored over water stabilization for certain crosslinkers. Under ambientconditions small particles have been observed to develop in some ofthese ink examples.

At high equivalent ratios of electrophilic crosslinkers withcarboxylated polymers, the crosslinking reaction is favored and theresulting examples gelled or solidified in solution during the keepingperiod. This gelling and solidification behavior of inks duringaccelerated keeping at elevated temperatures was observed in Example ink43 as shown in Table 12.

For such crosslinkers at such concentrations as found in these examples,water stabilization was not sufficient to create a stable equilibriumbetween the reactants. Example ink 43 used 0.2 equivalents ofcrosslinker for every one equivalent of carboxylated in the resin ofthese examples. The concentration of an individual electrophiliccrosslinker must be adjusted to ensure that the water stabilization ofthe crosslinking reaction remains favorable for long term ink keepingstability.

Example inks 38 to 49, as shown in Table 18 of FIG. 18, were assessedfor stability by measuring the change in their particle size. Forexample, the particle size distribution (PSD) of Example ink 39 wasmeasured after 3 days at ambient keeping, the largest observed PSD peakhas a mean particle size of 184 microns.

These ink examples were characterized for PSD by using a disposablemicropipette to dispense sufficient ink into the 180 ml of RODI water inthe Vortex Genie and flow cell until the light transmittance of theinstrument dropped to 60%. This typically required about 3 ml of theun-pigmented ink. PSD measurements are reported as 50th percentilefraction (D50) below a given particle size (μm). Fresh samples showed nolight scattering indicating at all ink components were dissolved in theink vehicle. After 3 days of ambient keeping, particles (3-184 μm) wereobserved to form in all but Example ink 45. Example ink 45 contains anucleophilic crosslinker.

The equivalents of organic electrophilic crosslinkers to nucleophiliccarboxylate groups in the resin is preferably less than 100%, morepreferably less than 50%, most preferably less than 25%.

Example inks 50 to 59 are shown in Table 19 of FIG. 19. Example inks 50to 58 were prepared to demonstrate that carboxylated polymers may beneutralized with a variety of bases and maintain good ink keepingstability. Example inks 50-52 were prepared with ammonium hydroxideneutralized Joncryl 683. Example inks 53-55 were prepared withtriethanol amine (TEA) neutralized Joncryl 683. Example inks 56-58 wereprepared with dimethylethanol amine (DMEA) neutralized Joncryl 863. As apoint of comparison, Example inks 1, 3, and 4 (FIG. 1) were preparedwith potassium hydroxide neutralized Joncryl 683.

For example, example ink 51 was prepared by combining 10 g of anammonium neutralized Joncryl 683 stock solution (20% solids) with 6 g ofglycerol, 12 g of 2-pyrrolidone, 0.3 g of Surfynol 440, 0.3 g ofCapstone FS-31, 0.02 g of Proxel GXL, and 0.13 g of Epocros WS-700.

Example inks 50 to 59, as shown in Table 20 of FIG. 20, were assessedparticle size and viscosity stability.

For example, Example ink 54 was evaluated for particle size andviscosity stability. The initial average particle size was 60 nm, thisdecreased to 56 nm after 4 weeks and 57 after 8 weeks conditioning at60° C. The initial viscosity of Example ink 54 was 2.45 cP. This changedto 2.47 cP after 4 weeks and 2.44 cP after 8 weeks conditioning at 60°C. Example ink 54 was judged to have excellent stability.

Example inks 50-54 and 56 had excellent viscosity stability. Example ink55 had fair viscosity stability. Example ink 57 had very good viscositystability, and Example ink 58 had poor viscosity stability (Table 20 ofFIG. 20) after conditioning for 8 weeks at 60° C. Example inks 50-58 hadexcellent particle stability (Table 20 of FIG. 20) after conditioningfor 8 weeks at 60° C.

Example ink 59 was prepared and charged into an Epson Stylus piezoinkjet printer and 8 full bleed pages were printed, utilizing 24 g ofink, without issue.

An ink was prepared in a similar fashion to Example ink 2 with theexception that the 12% black pigment dispersion was replaced with 9.5%of Kodak™ Specialty Cyan P2 pigment dispersion; the 2-pyrrolidone wasincreased from 12 to 25%; the 6% glycerol was replaced with 8%2-methyl-1,3-propanediol and 0.6 triethanol amine; the 0.3% CapstoneFS-31 was replaced with 0.32% Capstone 3100; 0.1% of Crodafos 03Aanti-kogation agent was added; and the reverse osmosis deionized waterwas decreased to 48.98%. This ink was used in a printing process,utilizing a HP™ Officejet Pro 8000 thermal ink-jet printer, withoutissue.

The inkjet ink for printing outdoor durable images on a inkjet printercomprising a basic pH aqueous ink vehicle, a soluble base, at least onewater soluble organic solvent with a boiling point above 200° C., apigment dispersion, a copolymer comprising carboxylic acid groups with aglass transition temperature above 60° C. and an acid number between 50and 400 mg KOH/g dissolved in the vehicle wherein the carboxylic acidgroups are base neutralized, a poly-electrophilic functionalizedcompound capable of crosslinking the carboxylic acidic groups on thecopolymer wherein the ratio of the poly-electrophilic groups on thefunctionalized compound to carboxylic acid groups on the copolymer is1:0.5 or less on an equivalent basis, the ink maintains a stableviscosity for a minimum of 4 weeks at 60° C. and the water in the inkinhibits the crosslinking reaction until after the ink is printed andthe water is substantially removed from the ink by drying.

An inkjet ink for printing images with an inkjet printer comprises abasic pH aqueous ink vehicle including water, a soluble base, and atleast one water soluble organic solvent; a pigment dispersion; and apolymer including base neutralized carboxylic acid groups with a glasstransition temperature between 0° C. and 150° C. and an acid numberbetween 50 and 1000 mg KOH/g dissolved in the vehicle, wherein thecarboxylic acid groups are base neutralized; a poly-electrophilicfunctionalized compound capable of crosslinking the neutralizedcarboxylic acidic groups on the polymer wherein the ratio of thepoly-electrophilic groups on the functionalized compound to carboxylicacid groups on the polymer is 1:1 or less on an equivalent basis and theink maintains a stable viscosity and pigment particle size distributionfor 6 weeks at 60° C.; the water in the ink inhibiting the crosslinkingreaction until after the ink is printed and the water is substantiallyremoved from the ink by drying; the ink does not contain tertiaryamines.

The polymer may be a polystyrene-co-acrylate polymer resin binder.

The poly-electrophilic functionalized compound may be a beta hydroxyamide crosslinker, an oxazoline functionalized reactive polymercrosslinker, a highly methylated, monomeric melamine crosslinker, anisocyanate crosslinker, a multifunctional type aliphatic epoxycrosslinker, a polyfunctional aziridine liquid crosslinker, a polymericcarbodiimide crosslinking agent, an organic titinate crosslinker, anorganosilane crosslinker, or a glycidyl ether crosslinker.

The at least one water soluble organic solvent maybe a humectant. Theinkjet ink may further comprise a surfactant, a first surfactant tomodify static surface tension and a second surfactant to modify dynamicsurface tension, and/or a biocide.

The soluble base may be a non-volatile base. The pH of the basic pHaqueous ink vehicle may be between 7 and 10. The soluble base may beammonia.

The polymer may be a soluble copolymer. The polymer may not be adispersed polymer. The polymer may not be a latex.

The poly-electrophilic functionalized compound may include at leastthree reactive groups. The polymer may be less than 10% of the ink byweight. The polymer may have a molecular weight less than 50,000. Theacid number may be between 50 and 400.

The water soluble organic solvent may be less than 50% of the ink byweight. The water soluble organic solvent may be less than 30% of theink by weight.

The average particle size of the pigment in the pigment dispersion maybe less than a micron. The pigment dispersion may be less than 20% ofthe ink by weight. The pigment dispersion may be less than 10% of theink by weight.

The viscosity may change less than 20% in 6 weeks at 60° C. Theviscosity may change less than 10% in 6 weeks at 60° C. The pigmentparticle size distribution may change less than 200 nm in 6 weeks at 60°C. The pigment particle size distribution may change less than 50 nm in6 weeks at 60° C.

The ratio of the poly-electrophilic groups on the functionalizedcompound to carboxylic acid groups on the polymer may be 0.5:1 or lesson an equivalent basis. The inkjet ink may be for printing images onnon-coated surfaces.

An inkjet ink for printing images with a thermal inkjet printercomprises a basic pH aqueous ink vehicle including water, a solublebase, and at least one water soluble organic solvent; a buffer; apigment dispersion; and a polymer including base neutralized carboxylicacid groups with a glass transition temperature between 0° C. and 150°C. and an acid number between 50 and 1000 mg KOH/g dissolved in thevehicle, wherein the carboxylic acid groups are base neutralized; apoly-electrophilic functionalized compound capable of crosslinking theneutralized carboxylic acidic groups on the polymer wherein the ratio ofthe poly-electrophilic groups on the functionalized compound tocarboxylic acid groups on the polymer is 1:1 or less on an equivalentbasis and the ink maintains a stable viscosity and pigment particle sizedistribution for 6 weeks at 60° C.; the water in the ink inhibiting thecrosslinking reaction until after the ink is printed and the water issubstantially removed from the ink by drying.

The polymer may be a polystyrene-co-acrylate polymer resin binder.

The poly-electrophilic functionalized compound may be a beta hydroxyamide crosslinker, an oxazoline functionalized reactive polymercrosslinker, a highly methylated, monomeric melamine crosslinker, amultifunctional type aliphatic epoxy crosslinker, a polymericcarbodiimide crosslinking agent, an organosilane crosslinker, or aglycidyl ether crosslinker.

The at least one water soluble organic solvent maybe a humectant. Theinkjet ink may further comprise a surfactant, a first surfactant tomodify static surface tension and a second surfactant to modify dynamicsurface tension, and/or a biocide.

The soluble base may be a non-volatile base. The pH of the basic pHaqueous ink vehicle may be between 7 and 10. The soluble base may beammonia.

The polymer may be a soluble copolymer. The polymer may not be adispersed polymer. The polymer may not be a latex.

The poly-electrophilic functionalized compound may include at leastthree reactive groups. The polymer may be less than 10% of the ink byweight. The polymer may have a molecular weight less than 50,000. Theacid number may be between 50 and 400.

The water soluble organic solvent may be less than 50% of the ink byweight. The water soluble organic solvent may be less than 30% of theink by weight.

The average particle size of the pigment in the pigment dispersion maybe less than a micron. The pigment dispersion may be less than 20% ofthe ink by weight. The pigment dispersion may be less than 10% of theink by weight.

The viscosity may change less than 20% in 6 weeks at 60° C. Theviscosity may change less than 10% in 6 weeks at 60° C. The pigmentparticle size distribution may change less than 200 nm in 6 weeks at 60°C. The pigment particle size distribution may change less than 50 nm in6 weeks at 60° C.

The ratio of the poly-electrophilic groups on the functionalizedcompound to carboxylic acid groups on the polymer may be 0.5:1 or lesson an equivalent basis. The inkjet ink may be for printing images onnon-coated surfaces.

The inkjet ink may further comprise an anti-Kogation agent.

An inkjet ink for printing durable outdoor images with an inkjet printerconsists essentially of a basic pH aqueous ink vehicle including water,a soluble base, and at least one water soluble organic solvent; a staticsurface tension surfactant; a dynamic surface tension surfactant; abiocide; a pigment dispersion; and a polymer including base neutralizedcarboxylic acid groups with a glass transition temperature between 0° C.and 150° C. and an acid number between 50 and 1000 mg KOH/g dissolved inthe vehicle, wherein the carboxylic acid groups are base neutralized; apoly-electrophilic functionalized compound capable of crosslinking theneutralized carboxylic acidic groups on the polymer wherein the ratio ofthe poly-electrophilic groups on the functionalized compound tocarboxylic acid groups on the polymer is 1:1 or less on an equivalentbasis and the ink maintains a stable viscosity and pigment particle sizedistribution for 6 weeks at 60° C.; the water in the ink inhibiting thecrosslinking reaction until after the ink is printed and the water issubstantially removed from the ink by drying.

The polymer may be a polystyrene-co-acrylate polymer resin binder.

The poly-electrophilic functionalized compound may be a beta hydroxyamide crosslinker, an oxazoline functionalized reactive polymercrosslinker, a highly methylated, monomeric melamine crosslinker, anisocyanate crosslinker, a multifunctional type aliphatic epoxycrosslinker, a polyfunctional aziridine liquid crosslinker, a polymericcarbodiimide crosslinking agent, an organic titinate crosslinker, anorganosilane crosslinker, or a glycidyl ether crosslinker.

The at least one water soluble organic solvent maybe a humectant. Thesoluble base may be a non-volatile base. The pH of the basic pH aqueousink vehicle may be between 7 and 10. The soluble base may be ammonia.

The polymer may be a soluble copolymer. The polymer may not be adispersed polymer. The polymer may not be a latex.

The poly-electrophilic functionalized compound may include at leastthree reactive groups. The polymer may be less than 10% of the ink byweight. The polymer may have a molecular weight less than 50,000. Theacid number may be between 50 and 400.

The water soluble organic solvent may be less than 50% of the ink byweight. The water soluble organic solvent may be less than 30% of theink by weight.

The average particle size of the pigment in the pigment dispersion maybe less than a micron. The pigment dispersion may be less than 20% ofthe ink by weight. The pigment dispersion may be less than 10% of theink by weight.

The viscosity may change less than 20% in 6 weeks at 60° C. Theviscosity may change less than 10% in 6 weeks at 60° C. The pigmentparticle size distribution may change less than 200 nm in 6 weeks at 60°C. The pigment particle size distribution may change less than 50 nm in6 weeks at 60° C.

The ratio of the poly-electrophilic groups on the functionalizedcompound to carboxylic acid groups on the polymer may be 0.5:1 or lesson an equivalent basis. The inkjet ink may be for printing images onnon-coated surfaces.

It will be appreciated that the above-disclosed embodiments and otherfeatures and functions, or alternatives thereof, may be desirablycombined into many other different combinations. Also, various presentlyunforeseen or unanticipated alternatives, modifications, variations, orimprovements therein may be subsequently made by those skilled in theart which are also intended to be encompassed by the description aboveand the following claims.

What is claimed is:
 1. An inkjet ink for printing durable outdoor imageswith an inkjet printer consisting essentially of: a basic pH aqueous inkvehicle including water, a soluble base, and at least one water solubleorganic solvent; a static surface tension surfactant; a dynamic surfacetension surfactant; a biocide; a pigment dispersion; and a polymerincluding base neutralized carboxylic acid groups with a glasstransition temperature between 0° C. and 150° C. and an acid numberbetween 50 and 1000 mg KOH/g dissolved in the vehicle, wherein thecarboxylic acid groups are base neutralized; a poly-electrophilicfunctionalized compound capable of crosslinking the neutralizedcarboxylic acidic groups on the polymer wherein the ratio of thepoly-electrophilic groups on the functionalized compound to carboxylicacid groups on the polymer is 1:1 or less on an equivalent basis and theink maintains a stable viscosity and pigment particle size distributionfor 6 weeks at 60° C.; the water in the ink inhibiting the crosslinkingreaction until after the ink is printed and the water is substantiallyremoved from the ink by drying.
 2. The inkjet ink as claimed in claim 1,wherein said polymer is a polystyrene-co-acrylate polymer resin binder.3. The inkjet ink as claimed in claim 1, wherein said poly-electrophilicfunctionalized compound is a compound selected from the group consistingof a beta hydroxy amide crosslinker, an oxazoline functionalizedreactive polymer crosslinker, a highly methylated, monomeric melaminecrosslinker, an isocyanate crosslinker, an organic titinate crosslinker,an organosilane crosslinker, a glycidyl ether crosslinker, amultifunctional type aliphatic epoxy crosslinker, a polyfunctionalaziridine liquid crosslinker, or a polymeric carbodiimide crosslinkingagent.
 4. The inkjet ink as claimed in claim 1, wherein at least onewater soluble organic solvent is a humectant.
 5. The inkjet ink asclaimed in claim 1, further comprising a surfactant.
 6. The inkjet inkas claimed in claim 1, further comprising a first surfactant to modifystatic surface tension and a second surfactant to modify dynamic surfacetension.
 7. The inkjet ink as claimed in claim 1, further comprising abiocide.
 8. The inkjet ink as claimed in claim 1, wherein said solublebase is a non-volatile base.
 9. The inkjet ink as claimed in claim 1,wherein the pH of said basic pH aqueous ink vehicle is between 7 and 10.10. The inkjet ink as claimed in claim 1, wherein said polymer is asoluble copolymer.
 11. The inkjet ink as claimed in claim 1, whereinsaid polymer is not a dispersed polymer.
 12. The inkjet ink as claimedin claim 1, wherein said polymer is not a latex.
 13. The inkjet ink asclaimed in claim 1, wherein said poly-electrophilic functionalizedcompound includes at least three reactive groups.
 14. The inkjet ink asclaimed in claim 1, wherein said polymer is less than 10% of the ink byweight.
 15. The inkjet ink as claimed in claim 1, wherein said polymerhas a molecular weight less than 50,000.
 16. The inkjet ink as claimedin claim 1, wherein said acid number is between 50 and
 400. 17. Theinkjet ink as claimed in claim 1, wherein said water soluble organicsolvent is less than 50% of the ink by weight.
 18. The inkjet ink asclaimed in claim 1, wherein said water soluble organic solvent is lessthan 30% of the ink by weight.
 19. The inkjet ink as claimed in claim 1,wherein an average particle size of a pigment in said pigment dispersionis less than a micron.
 20. The inkjet ink as claimed in claim 1, whereinsaid pigment dispersion is less than 20% of the ink by weight.
 21. Theinkjet ink as claimed in claim 1, wherein said pigment dispersion isless than 10% of the ink by weight.
 22. The inkjet ink as claimed inclaim 1, wherein the viscosity changes less than 20% in 6 weeks at 60°C.
 23. The inkjet ink as claimed in claim 1, wherein the pigmentparticle size distribution changes less than 200 nm in 6 weeks at 60° C.24. The inkjet ink as claimed in claim 1, wherein the pigment particlesize distribution changes less than 50 nm in 6 weeks at 60° C.
 25. Theinkjet ink as claimed in claim 1, wherein the ratio of thepoly-electrophilic groups on the functionalized compound to carboxylicacid groups on the polymer is 0.5:1 or less on an equivalent basis. 26.The inkjet in as claimed in claim 1, wherein the inkjet ink is forprinting images on non-coated surfaces.
 27. The inkjet ink as claimed inclaim 1, wherein the viscosity changes less than 10% in 6 weeks at 60°C.
 28. The inkjet ink as claimed in claim 1, wherein said soluble baseis ammonia.